1. Field of the Invention
The present invention is directed to waveguides, and more particularly, to waveguides formed on a substrate.
2. Description of the Related Art
Light offers many advantages when used as a medium for propagating information, the foremost of which are increased speed and bandwidth. In comparison with electrical signals, signals transmitted optically can be switched and modulated faster and can include an even greater number of separate channels multiplexed together. Accordingly, lightwave transmission along optical fibers is widespread in the telecommunications industry. In an exemplary fiber optic communication system, a beam of light may be emitted from a laser diode and modulated using an electro-optical modulator that is driven by an electrical signal. This electrical signal may correspond to voice or data which is to be transmitted over a distance between, e.g., two components in a computer, two computers in a network, or two phones across the country or the world. The light travels in an optical fiber to a location where it is detected by an optical sensor which outputs voltage that varies in accordance with the modulation of the optical beam. In this manner, information can be rapidly transported from one location to another.
Accordingly, various components have been developed to process and manipulate optical signals. Examples of such components include modulators, switches, filters, multiplexers, demultiplexers to name a few. Other useful optical components include lasers and optical detectors as well as waveguides. Many of these components can be formed on a substrate. It is therefore highly desirable to combine a variety of such components into a system that is integrated onto a single substrate. In such a system, optical waveguides theoretically could be used to propagate optical signals between components on the substrate.
One aspect of the present invention comprises a strip loaded waveguide comprising a slab portion having a first refractive index n1, a strip portion having a second refractive index n2, and a transition portion between the slab portion and the strip portion. The transition portion has a refractive index n3 that is less than the first refractive index n1 and the second refractive index n2.
Another aspect of the present invention comprises a strip loaded waveguide comprising a slab portion and a strip portion. The strip portion is disposed with respect to the slab portion to form a guiding region. A first portion of the guiding region is in the strip portion, and a second portion of the guiding region is in the slab portion. The guiding region propagates light in a single spatial mode and only in a transverse electric mode.
Another aspect of the present invention comprises a strip loaded waveguide comprising a slab portion and a strip portion. The strip portion is disposed with respect to the slab portion to form a guiding region. A first portion of the guiding region is in the strip portion, and a second portion of the guiding region is in the slab portion. The guiding region propagates light in a single spatial mode with a cross-sectional power distribution profile having two intensity maxima. A first intensity maxima is located in the slab portion, and the second intensity maxima is located in the strip portion.
Another aspect of the present invention comprises a waveguide having a guiding region for guiding light through the waveguide. The guiding region comprises a layer of polycrystalline silicon juxtaposed with a layer of crystal silicon.
Yet another aspect of the present invention comprises an apparatus comprising a strip loaded waveguide, a transistor, and a substrate. The strip loaded waveguide comprises a slab portion having a first refractive index n1, a strip portion having a second refractive index n2, and a transition layer between the slab portion and the strip portion. The transistor comprises first and second portions and a dielectric layer therebetween. The dielectric layer of the transistor and the transition layer of the waveguide comprise the same material. The substrate supports both the transistor and the waveguide.
Yet another aspect of the present invention comprises an apparatus comprising a strip loaded waveguide, a transistor, and a substrate. The strip loaded waveguide comprises a slab portion having a first refractive index n1 and a strip portion having a second refractive index n2. The transistor comprises first and second portions and a dielectric layer therebetween. The second portion of the transistor and the slab portion of the waveguide are formed of a single layer of material. The substrate supports both the transistor and the waveguide.
Still another aspect of the present invention comprises a method of changing the index of refraction of a strip loaded waveguide comprising a semiconductor slab and a conductive strip that are separated by an insulating layer. The method comprises dynamically changing the carrier distribution in the semiconductor slab.
Still another aspect of the present invention comprises a waveguide apparatus. The waveguide apparatus comprises a slab portion having a first refractive index, a strip portion having a second refractive index, and a transition portion between the slab portion and the strip portion. The transition portion has a third refractive index that is less than the first refractive index and the second refractive index. The waveguide apparatus additionally comprises a voltage source configured to apply a voltage between the strip portion and the slab portion such that an electric field is introduced between the strip portion and the slab portion.